Bull Shark

The Bull shark is a massive shark that can reach a length of 3.5 metres and weigh more than 315 kg. The females are usually larger than the males. The body is compact with a snout that is short and broad which gives it a somewhat blunt appearance. The eyes are comparatively small and the body is without interdorsal ridge. The characteristic first dorsal fin is wide and has a triangular shape. It is usually 3.2 times the height of the second dorsal fin. The bull shark sports greyish colours above and a white belly. The fins have darker tips that are particularly visible in juvenile sharks. The upper teeth of the Bull shark are triangular and saw-edged. The oldest known Bull Shark was 32 years old.

The Bull shark, Carcharhinus leucas, is known by several other names, including River Shark, Estuary Whaler, Freshwater Whaler, Swan River Whaler, Ground shark, Slipway Grey, Zambezi and Shovelnose. There are only six known shark species in the world capable of living in both salt and fresh water: the Borneo river shark (Glyphis sp. B), the Irrawaddy river shark (Glyphis siamensis), the New Guinea river shark (Glyphis sp. C), the Ganges shark (Glyphis gangeticus), the Speartooth shark (Glyphis glyphis) and the Bull shark (Carcharhinus leucas). The Bull shark is the most common of these six species and is found in many different parts of the world.

In the Western Atlantic, you can find Bull shark from off the coast of Massachusetts, USA and down to southern Brazil. On the Eastern side of the Atlantic the Bull shark lives off the coast of Morocco and from Senegal to Angola. The Bull shark is also found in the Indo-West Pacific where it inhabits the region from Kenya and South Africa to India, and further into the waters around Australia and Vietnam. On the Western side of the South- and North American continents the Bull shark lives from southern Baja California in Mexico and down to Ecuador. Bull shark might also have been sighted off the coast of Peru, but this is still not confirmed.

The Bull shark prefers to stay close to the coast and lives in shallow waters, such as bays and estuaries. Since it can survive in fresh water it will often swim up rivers and streams, and can even enter lakes. The young Bull sharks are particularly found of fresh water and are sometimes found hundreds of kilometres from the ocean in rivers and streams. The adult Bull sharks prefer the region where fresh water rivers empty into the sea, such as river deltas and estuaries. Bull sharks seldom dive deeper than 30 m and are commonly found in much shallower waters where the depth is just a few metres. This preference for shallow waters very close to the coastline and silent bays means that the Bull sharks have to share their habitat with humans in most parts of the world. This is also why the Bull shark is considered one of the most dangerous shark species and has been involved in a series of attacks on humans. The Bull shark should always be approach with caution, and preferably not approached and disturbed at all if possible. Its reputation as a vicious human eating beast is however completely undeserved.

The Bull shark hunts alone and feeds primarily on bony fishes and other sharks. Small Sandbar sharks are particularly popular, but the Bull shark is an opportunist and will eat a wide range of food, including rays, sea turtles, mammalian carrion, mantis shrimps, squids, crabs, sea urchins, sea snails and even garbage.

A Bull shark will reach sexual maturity when it is between 8 and 10 years old. The Bull shark's reproductive method is viviparous. The eggs are fertilized inside the female Bull shark and develop inside her, receiving nutrition from a yolk-sac placenta. After a gestation period of approximately 10 or 11 months she gives birth to live pups. During courtship, the male embraces the female and female Bull sharks will therefore often have courtship scars on their bodies. Male bull sharks are almost always without fighting scars. One litter typically consists of 1-13 pups and a young Bull shark is usually around 60 cm long at birth. The time of birth is depending on the habitat of the female Bull shark. For example, females Bull sharks living off Nicaragua can give birth year round, with the number of births peaking in spring and early summer. Female Bull sharks living off the South African coast on the other hand will only give birth in late spring or early summer. The same thing is true for female Bull sharks living in the western North Atlantic outside Florida or in the Gulf of Mexico. The minimum population doubling time for Bull sharks exceeds 14 years.

The Bull shark is a sturdy fish that can be successfully kept in captivity and it is frequently found in public aquariums. It is also hunted for consumption by humans. The meat is eaten fresh, frozen or smoked, while the fins are popular in shark fin soups. Other parts of the Bull shark are also utilized, such as the hide that is turned into leather, the liver which is appreciated for its oil and the remaining carcass which is commonly used to produce fish food. It also frequently caught in fisheries without being the true target species. The Bull shark is especially vulnerable to human impact since it like to stay close to land and shares the same habitats as we do. The average size of Bull sharks caught by the Natal Sharks Board has decreased considerably and there is some concern regarding the status of the Bull shark, but it is only considered lower risk - near threatened by CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora. The Bull shark is however included in the IUCN Red List of Threatened Species. (IUCN has today changed its name from “International Union for the Conservation of Nature and Natural Resources” to “The World Conservation Union”, but the acronym IUCN is still used for the Red List.)

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